1. Field of the Invention
The invention is related generally to the field of numerically controlled machines for machining parts in accordance with a prepared program and, in particular, the invention relates to an auxiliary processor in the form of a programmable interface controller assuming specific sequential control functions.
2. Prior Art
The advent of electronic computers for accurately solving complex problems in a quick and efficient manner has led to the rapid development of numerically controlled machines for making limited numbers of relatively complex parts. These numerical control machines basically comprise a program reader, a controller, an input/output interface and a machine being controlled. A set of instructions, called a program, is prepared and permanently recorded on a convenient recording media, such as magnetic or punched tape. The program reader reads the recorded program and translates the recorded instructions into electrical signals compatible with the controller. The controller, in the form of an electronic numerical control computer, responds to the signals from the program reader and signals indicative of the state of the machine and generates signals to control the machine to perform each set of instructions contained in the program in their proper sequence. In the course of the development of numerical control machines, it has been found that many sequential functions can be controlled more efficiently and expeditiously by an auxiliary processor rather than embodying these functions in the computer or in the program itself. The auxiliary processor acquires input data from the normal input and output devices associated with the machine, as well as those provided by the numerical control computer and analyzes this information by performing logical arithmetic on the status of the various inputs and outputs and generates appropriate output signals as a result. The output signals may be directed to the numerical control computer, to the machine through an appropriate interface or both. The output signals may be directed to the numerical control computer, to the machine through an appropriate interface or both. The output signals directed to the numerical control computer are used to activate switches or status lights on the control panel while the output signals directed to the machine itself activates solenoids, relays, lights, motors, etc., as may be necessary or desired.
The first generation of auxiliary processors were multiple contact relay and/or discrete solid state switch networks handwired according to the various arithmetic logic functions desired. These handwired networks usually referred to as "magnetics", although fairly complex and relatively expensive, were still less expensive than if these same functions were embodied in the program or in the control computer. These auxiliary processors substantially reduced the storage requirements and work load of the control computer. It has been found that whenever there is a significant change in the auxiliary processor, it is more economical and expedient to construct a new network rather than rewire the old one. These handwired auxiliary processors still remain relatively expensive, time consuming and undesirable from a cost effective point of view.
The present generation of auxiliary processors have switched from the handwired multiple contact relay or discrete solid state switch networks discussed above to electronically programmable controllers. T. J. Markley, in U.S. Pat. No. 3,810,104 "Programmable Magnetics for a Numerical Control System" (May 7, 1974), discloses a programmable interface controller serially disposed between the numerical control computer and the machine and performs both conventional computer interface functions, as well as the auxiliary processor functions of the prior art "magnetics". The Markley system further receives and stores auxiliary inputs from the numerical control computer which are utilized in the programmed operation to operate the machine tool input devices. The system disclosed by Markley, however, does not utilize the full potential of a programmable controller, such as disclosed by W. H. Seipp in U.S. Pat. No. 3,827,030 "Programmable Controller Using a Random Access Memory" (July 30, 1974) and in the publications cited therein. This type of programmable controller has expanded capabilities and may also be used to make routine calculations normally performed by the numerical control computer, as well as performing the control functions of the prior art auxiliary processors. These factors would both simplify the program and reduce the work load on the numerical control computer.
The invention is an improved electronically programmable controller interfacing the numerical controlled computer through a bi-directional bus capable of performing additional sequential control functions, as well as those functions performed by the conventional relay or discrete solid state functions discussed above.